Dismiss Notice

Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

Mistake? Or Not?

Discussion in 'Amps and Cabs [BG]' started by bentem, Mar 15, 2003.


  1. bentem

    bentem

    Oct 18, 2002
    Rockville, MD
    I bought a old peavy m-3000 power amp(which you might have heard me complaining about before) that i bought at guitar center. It runs 300 watts at 2ohms(im not sure bridged or sterio), and 210 at 4ohms.

    So i bought a avatar b210, but i got the 4ohm version, hoping to add another 4ohm 115 to get the full power out of the amp. Except the amp is a peice of junk(i paid $105 for it)

    My question is this- if I buy the next cabinet, and the peavy amp dies, or i cant standd it anymore, or i need more power, will i be able to find a poweramp or a head that runs 2ohms, preferably bridged mono, unless running it in sterio is not too difficult and will not change the tone

    I was planning on buying a rackmounted preamp next week, i just wanted to make sure this rig is worth investing any more money into, or if i should switch to 2 8ohm cabs instead if 2 4ohm cabs
     
  2. eli

    eli Mad showoff 7-stringer and Wish lover Supporting Member

    Dec 12, 1999
    NW suburban Chicago
    Your M-3000 is a mono amp, not stereo, so there's no bridged option.

    Which 115 spk would you get? With a 4 ohm 210 and a 4 ohm 115, I would think your best power amp choice would be a stereo amp that puts 250 watts (or more) per side into 4 ohms. Of course, to use that, you'd need a crossover. What's your preamp?

    One interesting point about bi-amping bass: the high side needs only about 1/4 to 1/3 the power of the low side. There's a bi-amp bass amp on the market (can't remember whose -- GK, perhaps?) that has a low side rated 350 watts into 4 ohms, coupled to a high side that is only 50 watts into 8 ohms. This thing works because the human ear is far more sensitive to mids and highs than it is to lows, so you need lots more power in the lows to balance the apparent loudness of the mids and highs. This is also why a bassist usually needs 250 watts or more to compete with a guitarist playing through a cranked 50-watt combo.

    There are pretty few stereo power amps that are stable bridged mono down to 2 ohms, but there are a few.

    I'm a Carvin fan, and I haven't seen any amps that can match the "power-to-bucks" ratio of their R1000: 350 watts per side into 4 ohm loads for $650. Or the power amp DCM1000 which is 300 watts per side into 4 ohms for $360.

    Of couse, you can always get better prices second hand, but you better know what you're looking at if there's no warranty.

    Let us know what you wind up with.
     
  3. bentem

    bentem

    Oct 18, 2002
    Rockville, MD
    for a 15, i would probaly get an avatar b115, to match my 210.

    Theres a used store about a half hour away from my house, and i was probaly going to go there to find a preamp. I also was looking at the carvins and the 600 and 1000 bass heads run sterio at 2ohms.

    But i dont really understand how biamping/stero works. Will i have to put to put the lows one way, and the highs another? or is there something else i can do?
     
  4. eli

    eli Mad showoff 7-stringer and Wish lover Supporting Member

    Dec 12, 1999
    NW suburban Chicago
    OK:

    Bi-amping is splitting the preamp signal into low frequencies and high frequencies (the electronics that does this is called a crossover), then sending these two separate signals to two separate power amps. Crossovers usually have a knob that allows you to adjust the frequency at which the signal is split. Then each power amp works independently to drive its own separate speaker array. Each power amp has a power/load rating, like 250 watts into 4 ohms, for example.

    Stereo bass amps (like the Carvins) have all of this suff hooked up inside one box, with all of the required output jacks right on the amp. Some also have switches for bridging the two amps into one output (that's how I run my R600, with my single 1x15 cab), but not all stereo bass amps have this "bridged-mono" capability.
     
  5. bentem

    bentem

    Oct 18, 2002
    Rockville, MD
    do most preamps have a crossover? and how do i know how/at what frequency to split the signal?
    if i have a poweramp that is 2ohms sterio, and has a bridged switch, can i run it 2ohms bridged?

    btw, thanks for all the help
     
  6. eli

    eli Mad showoff 7-stringer and Wish lover Supporting Member

    Dec 12, 1999
    NW suburban Chicago
    If a preamp says it is "biampable" or "Biamp capable", then it has a crossover. To make sure, check to see that it has two output jacks labeled "Hi out" and "Lo out" or some such. Almost all preamps that have a crossover have a crossover frequency knob.

    You choose the crossover frequency simply based on what sounds best to you. Say you have a 115 for the lows and a 210 for the highs. When you turn the knob to 800 Hz, this means that everything above 800 Hz will go to the 210, and everything below 800 Hz will go to the 115. If you turn the knob to 200 Hz, then everything above 200 Hz will go to the 210 and everything below 200 Hz will go to the 115. The difference in sound will be the fact that the 115 will treat that spectrum between 800 and 200 Hz differently than the 210 would. Also, you will probably have the low side turned up higher than the high side, so more or less of that mid spectrum will go to the 115. This will change your tone, and will not hurt anything; the two power amps are acting independently and only interacting with their speaker cabinets. From the user's standpoint (that's you), you just set it where you think it sounds good.

    If a power amp is 2 ohms stereo, that means it has two separate power amps inside, and EACH power amp (separately) is rated stable down to a 2 ohm load. USUALLY (check the specs) amps like this will only be stable in bridged mono mode down to 4 ohms. This is precisely the case with the Carvins we have been talking about. YOU MUST READ THE SPECS for the amp, and be sure that you will not be hooking it up to a lower load (ohms, impeadance, and load all mean the same thing) than it can handle with the speakers that you own. Note that as soon as you bridge mono, you lose the biamp (independent high and low control) capability, and the full range signal will be sent to all of the speakers that you hook up. This is not necessarily either good or bad, it's just different, and you need to know this to avoid cooking the amp. Again, many amps (read those specs!) have cutoff circuits that simply shut off the amp if the load is too low.

    SO: If you buy that 4-ohm 115, you will have two 4-ohm cabinets. Let's say you buy a Carvin R600. If you hook the up in biamp mode, you will have each amp powering a 4-ohm load, which is just fine. BUT if you bridge mono and plug BOTH speakers into the amp, you would produce a 2-ohm load which is too low for the amp in bridged mono mode; it would shut itself off to protect itself from self-destruction. So you do, indeed, need to know what you are doing, even with the same amp and the same two speakers.

    For reference, here's that Carvin:

    http://www.carvin.com/cgi-bin/Isearch.exe?CFG=2&P2=R600&P1=BA

    BTW, just because an amp has two speaker outputs does NOT mean it is a stereo (2-amp) amplifier. If a mono amp (like your M3000) has two output jacks, they will connect the two speakers in parallel.
     
  7. Wes Whitmore

    Wes Whitmore Supporting Member

    Mar 10, 2003
    Columbus, OH
    THe GK does offer a biampable option, but I am almost positive that the 50 watt channel is only made to power the tweeter/horn. The internal xover is really high, around 3KHz or higher. It isn't designed to run the midbass 4x10 cab or anything like that. There is no adjustable xover freq either.
     
  8. rok51

    rok51

    Sep 2, 2002
    Crawfordville, FL
    There are pretty few stereo power amps that are stable bridged mono down to 2 ohms, but there are a few.

    That would be equivalent to one ohm in stereo. I don't know of any amp that is rated at one ohm stereo/two ohms, bridged.

    If I am wrong, I'd love to be corrected.:)

    I would suggest two 8 ohm cabinets for the versatility. Right now, high-power amps are cheaper and more plentiful than ever. With a stereo amp (QSC, Yamaha, Crown, Peavey, Stewart, etc) you have the option of running bridged mono into one 8 ohm cab, bridged mono into two 8 ohm cabs (with most of the above amps) or stereo into either one or two 8 ohm cab per side. In short, it would be much more versatile, regardless of your compliment of cabinets. In the past Peavey's optimizing their amps to put maximum power into 2 ohms made sense. It no longer does.

    Kim
     
  9. These are your options:
    1. buy a mono bass amp head that will work at 2 ohms. and there are several.
    2. Buy a Stereo amp and run it full range dual mono or add a x-over and bi-amp. I think that Crown Macro Tech is stable at 2 ohms bridged but the cost and weight might be prohibative. jmho
     
  10. bentem

    bentem

    Oct 18, 2002
    Rockville, MD
    I think for now, i might just buy a preamp and run the peavy bridged mono into my 210 untill i get the 115, and then i'll run it bridged mono from the peavy untill i get a new poweramp, and ill run it in sterio.

    its a neverending cycle:D :D
     
  11. eli

    eli Mad showoff 7-stringer and Wish lover Supporting Member

    Dec 12, 1999
    NW suburban Chicago

    I repeat: According to the manual on the website, the M-3000 is a mono, NOT a stereo amp; it does not have the capability to run in "bridged mono" mode. You will NOT be able to run two cabinets in stereo with the M-3000. It is a mono amp, and that's all you can do with it. You can plug two cabinets into it, but they will both get the same signal; that is NOT "stereo".

    I am not quite sure what would happen if you plugged two signals into the two input jacks. You will NOT in any event get lows out of one speaker output and highs out of the other.
     
  12. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    They're not far away. There is a brand called "Camco" who make them but they cost as much as a car. They run at something rediculous, 10,000w at 1 ohm bridged mono. Thats when the price tag starts to make sense. I saw one of these amps running a whole bank of subs of a Martin wavefront PA. You'de normally need 3 or 4 amps to do that.

    Bentem, why don't you run a parallel link from the 2x10 to the 1x15. That's a 2 ohm load.
     
  13. bentem

    bentem

    Oct 18, 2002
    Rockville, MD
    What i meant was that i would run the peavy mono at 2ohms, . Then when i get a new poweramp, i would get one that runs in sterio and do that. Sorry for the confusion
     
  14. eli

    eli Mad showoff 7-stringer and Wish lover Supporting Member

    Dec 12, 1999
    NW suburban Chicago
    Cool.

    What preamps are you looking at? Do they have crossovers?

    Petebass,

    "Bentem, why don't you run a parallel link from the 2x10 to the 1x15. That's a 2 ohm load."

    The M3000 has two parallel output jacks that accomplish the same thing, without having to put an additional jack on either cab.
     
  15. bentem

    bentem

    Oct 18, 2002
    Rockville, MD
    well, i was looking at the sansamp RBI, but there is that store that i mentioned before. Its called Atomic Music, and its a guitar center-sized store thats all used. You never know what you might find , so i was thinking of going there.

    RockBobby here at TB offered me an eden navigator, but its a little bit above my price range. Im still considering it, though

    Those carvins are starting to look nice, too
     
  16. The power amp is only a portion of the overall sound you get (and a relatively small portion at that, provided you get enough power--and 210 watts into 4 ohms should be plenty)...What are you driving the amp with now? Preamp. or out of another head or combo, or?? (Surely you're not just plugging your bass into the high-Z jack.) How are you setting your EQ going to your power amp?

    But it sounds like you've already decided you don't like this amp. Too bad, cause I doubt it's the amp's fault. Garbage in=garbage out. :(
     
  17. eli

    eli Mad showoff 7-stringer and Wish lover Supporting Member

    Dec 12, 1999
    NW suburban Chicago
    Be sure to look at ebay! Carvin R600's are selling between $325 and $380, and an R1000 just sold at BuyItNow for $400. Might even find one at Atomic!
     
  18. bentem

    bentem

    Oct 18, 2002
    Rockville, MD
    well, actually, im not using it at all right now. I was using a pandora px4b but that didnt prouce a hot enough signal to drive the amp. I wasnt very loud, and when i turned the poweramp above like, 6 or 7 it would start to get distorted.

    I'll look into those carvins on ebay